Swiss prosecutors have searched offices of the Geneva subsidiary of HSBC bank in an inquiry into alleged money-laundering.

They said they were investigating HSBC Private Bank (Suisse) and "persons unknown for suspected aggravated money laundering".

The investigation could be extended to people suspected of committing or participating in money laundering.

HSBC said it was "co-operating with the Swiss authorities."

The raid comes more than a week after allegations first emerged that HSBC's Swiss private bank may have helped wealthy clients evade tax.

HSBC published a full-page advert in several weekend papers containing an apology over the claims.

The chief executive of HSBC's Swiss private bank, Franco Morra, said last week it had shut down accounts from clients who "did not meet our high standards".

Mr Morra added the revelations about "historical business practices" were a reminder that the old business model of Swiss private banking was no longer acceptable.

Criminal investigation

HM Revenue & Customs was given the leaked data in 2010 and has identified 1,100 people who had not paid their taxes.

Last week, HSBC admitted that it was "accountable for past control failures", but said it had now "fundamentally changed".